Polyesters, polyamides, polyimides, polycarbonates and polyurethanes are used for various purposes because they have excellent mechanical properties. Since these polymers have a hydrolyzable ester bond, amide bond, imido bond, carbonate bond and urethane bond in the molecule, respectively, there may occur a problem with reliability when they are used in a more severe environment, and urgent countermeasures against this are awaited.
Since the catalytic hydrolysis of a hydrolyzable bond such as an ester bond is promoted when a polar group such as a carboxyl group is existent in the molecule, there is proposed a method of suppressing this disadvantage by using a sealing agent for the carboxyl group to reduce the carboxyl group concentration (Patent Document 1 and Patent Document 2).
As the sealing agent for an acid group such as a carboxyl group is used a mono- or poly-carbodiimide compound in consideration of the stability and reactivity of the sealing agent and the color of the obtained product, and some effect is obtained. However, as the mono- or poly-carbodiimide compound is a linear carbodiimide compound, a volatile isocyanate compound is by-produced at the time of its use, causing such an essential defect as the production of a bad smell, thereby deteriorating the work environment. The development of a sealing agent having higher reactivity and free from this defect is awaited.
Patent Document 3 discloses a macrocyclic carbodiimide compound having an urethane bond and a polymer chain with a molecular weight of 100 to 7,000. Since the macrocyclic carbodiimide compound has a high molecular weight, it has low efficiency as a sealing agent for acid groups. Patent Document 3 does not take into consideration the prevention of the production of a bad smell.    (Patent Document 1) JP-A 2004-332166    (Patent Document 2) JP-A 2005-350829    (Patent Document 3) WO2008/081230